As is known, frames for strollers and prams are currently widely used which can be folded so as to be able to pass from an extended (or open) condition, used to carry the child, to a collapsed (or closed) condition, in which the frame occupies less space and accordingly is easier to transport.
The most widely used folding frames include those commonly known as “umbrella-folding” due to the particular way in which they close.
Such frames for strollers or prams in fact fold both transversely and longitudinally (therefore along three dimensions) until they assume, in the collapsed condition, a shape which can be likened to the shape of a closed umbrella.
There are also frames which can fold with a so-called “flat-folding” closure and fold only longitudinally (along two dimensions).
In greater detail, a folding frame is constituted by a supporting framework which comprises two lateral side members, each of which is constituted by at least two uprights (front and rear ones), which support rotatably a wheel or a wheel assembly; the front uprights are further associated with a respective handle tube which supports, at one of its ends, a handgrip (or handle).
The front uprights and the rear uprights are articulated one another in order to allow the transition of the frame, as mentioned earlier, from the extended condition to the collapsed condition.
Usually, the handle tubes of one side member are connected to the rear uprights of the other side member by means of a crosspiece (commonly known as lower crosspiece) which, during use, is arranged below the structure adapted to accommodate the child to be carried.
As regards in particular umbrella-folding frames, the supporting framework has, between the two rear uprights, two pivoted parallelograms which are designed to allow the mutual approach and spacing, in a parallel manner, of the side members during transition from the extended condition to the collapsed condition and vice versa.
The folding frames, and particularly umbrella-folding ones, are very convenient to use, since they ensure a quick possibility to pass from the collapsed condition to the extended condition and vice versa and moreover occupy an extremely limited amount of space in the collapsed condition.